1. Field of the Invention
The invention relates to the field of prospecting and operating oil or gas wells in which rotary drill strings constituted by drill pipes and possibly other tubular components coupled end-to-end are used depending on the drilling requirements.
More particularly, the invention concerns a profiled part, such as a drill pipe, for rotary drilling equipment disposed in a drill pipe section or a heavy weight drill pipe or a drill collar or a drill stabilizer or a cross-over sub with a different diameter or thread type.
Such drill pipe sections associated with other components of the drill string (drill collars, stabilizers, etc) mean that in particular, deflected wells can be drilled, i.e. wells wherein the inclination with respect to the vertical or the horizontal can be varied during drilling. Deflected wells can currently reach depths of the order of 2 to 8 km and horizontal distances of the order of 2 to 15 km.
In the case of deflected wells comprising practically horizontal sections, the frictional torques due to rotation of the drill strings in the wells can reach very high values during drilling. The frictional torques may mean that the equipment used or the drilling objectives have to be reviewed. Further, it is very often difficult to lift the debris produced by drilling because of sedimentation of the debris produced in the drilled hole, in particular in the portion of the hole which is highly inclined with respect to the vertical. This results in poor cleaning of the hole and an increase in both the coefficient of friction of the drill pipes of the drill pipe section within the drilled hole and the contact surfaces between the drill pipes and the walls of the hole.
2. Description of the Related Art
FR-2 760 783 proposes a profile for a drill pipe with a collar which comes into contact with the wall of the drilled hole and which can remain stationary in rotation with respect to the wall, and grooved sections which can activate circulation of the drilling fluid.
More recently, FR-2 824 104 concerns a profiled element for rotary drilling equipment comprising a zone which bears on the wall of the drilled hole, a turbulence zone to produce activation of the circulation of a drilling fluid in the drilled hole around the drilling equipment, and a deflection zone adjacent to the bearing zone and to the turbulence zone extending in an axial direction of the profiled element and comprising at least one surface which is inclined with respect to the drilling axis, wherein the meridian line in an axial plane moves away from the axis of the profiled element in the direction moving from bottom to top in the service position of the profiled element in the drilled hole.
That type of device has proved satisfactory until recently. However, there is now a need to provide drill strings which are particularly robust, multifunctional and designed for drilling at considerable depths and at considerable departures.
The invention aims to improve the situation.